read -r does not protect backslashes

[Ian! D. Allen]

Edit: This isn't a bug in "read" - it's the way dash's "echo" handles backslashes.

Both natty and oneiric dash fail to protect backslashes when using "read -r".

natty: dash 0.5.5.1-7.2ubuntu1
oneiric: dash 0.5.5.1-7.4ubuntu1

Example bug:

    $ echo '000\n999' | dash -c ' read -r f ; echo "$f" '
    000
    999

Other shells do it correctly:

    $ echo '000\n999' | bash -c ' read -r f ; echo "$f" '
    000\n999

    $ echo '000\n999' | static-sh -c ' read -r f ; echo "$f" '
    000\n999

This means you can't use "read" to read arbitrary lines of text.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: dash 0.5.5.1-7.2ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-12.51-generic 2.6.38.8
Uname: Linux 2.6.38-12-generic x86_64
Architecture: amd64
Date: Sat Oct 22 18:28:32 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
SourcePackage: dash
UpgradeStatus: No upgrade log present (probably fresh install)

[Jilles Tjoelker (jilles)]

The backslash escape sequences are being processed by "echo", not "read". You can avoid this inconsistency by doing something like

printf "%s\n" '000\n999' | dash -c ' read -r f ; printf "%s\n" "$f" '

[Ian! D. Allen (idallen)]

Thanks Jilles - you are absolutely right. I had forgotten about versions of echo that process backslashes.
I see that one cannot turn off the backslash processing of the dash echo, which is why you need the printf.
Thanks!